This invention relates generally to the providing or supplying of inflation gas and, more particularly, to the providing or supplying of such inflation gas via an elongated inflator such as may be desired for certain inflatable passive restraint systems for use in vehicles for restraining the movement of an occupant in the event of a vehicular collision.
It is well known to protect a vehicle occupant by means of safety restraint systems which self-actuate from an undeployed to a deployed state without the need for intervention by the operator, i.e., “passive restraint systems.” Such systems commonly contain or include an inflatable vehicle occupant restraint or element, such as in the form of a cushion or bag, commonly referred to as an “airbag cushion.” In practice, such airbag cushions are typically designed to inflate or expand with gas when the vehicle encounters a sudden deceleration, such as in the event of a collision. Such airbag cushions may desirably deploy into one or more locations within the vehicle between the occupant and certain parts of the vehicle interior, such as the doors, steering wheel, instrument panel or the like, to prevent or avoid the occupant from forcibly striking such parts of the vehicle interior.
Various types or forms of such passive restraint assemblies have been developed or tailored to provide desired vehicle occupant protection such as based on either or both the position or placement of the occupant within the vehicle and the  direction or nature of the vehicle collision, for example. In particular, driver side and passenger side inflatable restraint installations have found wide usage for providing protection to drivers and front seat passengers, respectively, in the event of head-on types of vehicular collisions. Driver side and passenger side inflatable restraint installations do not, however, generally provide as great as may be desired protection against vehicular impacts inflicted or imposed from directions other than head-on, i.e., “side impacts.” In view thereof, substantial efforts have been directed to developing inflatable restraint installations having particular effectiveness in the event of a side impact.
Upon deployment, the time period during which an airbag cushion remains pressurized is commonly referred to as “stand-up time.” In practice, driver side and passenger side airbag cushions are typically desirably designed to begin deflating almost instantaneously upon deployment such as to avoid presenting an undesirably hard or ungiving surface to an oppositely situated vehicle occupant. However, airbag cushions which provide substantially longer stand-up times may be required or desired in the event of certain accidents or collisions in order to provide a suitable desired level of occupant protection. For example, one particularly troublesome form of side impact is commonly referred to as a “roll-over.” In a roll-over incident, a vehicle may undergo a partial, complete or multiple roll-over. As will be appreciated by those skilled in the art, roll-over accidents can be particularly demanding on inflatable restraint systems. In particular, an airbag cushion designed  to provide occupant protection in the event of a vehicle roll-over may be required or desired to remain pressurized for an extended or prolonged period of time, as compared to usual or typical driver side and passenger side airbag installations. For example, a roll-over protection side impact airbag cushion desirably remains pressurized or provides a stand-up time as long as about 5 seconds.
One particularly effective form of side impact inflatable restraint is the subject of HÅland et al., U.S. Pat. No. 5,788,270, issued 04 Aug. 1998, the disclosure of which patent is hereby incorporated by reference herein in its entirety and made a part hereof. Inflatable elements, such as disclosed in HÅland et al., U.S. Pat. No. 5,788,270, may desirably include an inflatable portion formed from two layers of fabric with the front layer and the back layer of the fabric woven together at selected points. In particular embodiments, such selected points are arranged in vertically extending columns and serve to divide the inflatable part into a plurality of vertical parallel chambers. The spaces between the selected points permit internal venting between adjacent chambers of the inflatable element. Particular such inflatable devices/elements, such as utilized in applications to provide protection over an extended area and having a generally planar form, are frequently referred to as “inflatable curtains.”
A one piece woven construction has been found to be a particularly effective method of forming such inflatable element airbag cushions. In particular, one piece woven constructions have been found to provide a relatively low cost  method of constructing suitable such airbag cushions which provide desired stand-up times. While inflatable element airbag cushions can, as is known in the art, be fabricated of various materials, nylon 6,6 has been found to be a particularly effective and useful material for use in the making or manufacture of inflatable curtain elements such as described above and having a one piece woven design.
In addition to an airbag cushion, inflatable passive restraint system installations also typically include a gas generator, also commonly referred to as an “inflator.” Upon actuation, such an inflator device desirably serves to provide an inflation fluid, typically in the form of a gas, used to inflate an associated airbag cushion. Many types or forms of inflator devices have been disclosed in the art for use in inflating an inflatable restraint system airbag cushion.
One particularly common type or form of inflator device used in inflatable passive restraint systems is commonly referred to as a pyrotechnic inflator. In such inflator devices, gas used in the inflation of an associated inflatable element is derived from the combustion of a pyrotechnic gas generating material. While various combustible pyrotechnic materials are available, gas generant compositions commonly utilized in the inflation of automotive inflatable restraint airbag cushions have previously most typically employed or been based on sodium azide.
The gas generated by the combustion of such pyrotechnic materials can be very hot and may contain variously sized particulate material. In practice, it is relatively common to include within such inflator devices a filter or the like effective  to remove such particulate and to reduce the temperature of the gas prior to discharge therefrom. Nevertheless, gas discharge temperatures in the range of about 1300 K are common for conventional pyrotechnic inflator devices. In view thereof, it is common to include within an associated airbag cushion a heat resistant coating or one or more strategically placed patches of heat resistant material such as to minimize or avoid direct contact of the hot inflator discharge onto unprotected airbag cushion material.
Further, pyrotechnic inflators, such as used for the inflation of passenger side airbag cushions, are commonly cylindrical in shape and typically have a length to diameter ratio (also commonly referred to as “L/D ratio”) in the range of about 7. In practice, the L/D ratios of such inflator devices have been limited or restricted by the general need or desire to ensure relative uniformity in ignitability over the length of the inflator device. In particular, it has proven difficult to attain ignition of an extended length of pyrotechnic gas generant material in a uniform manner while in an assembly of small diameter.
Another common form or type of inflator device utilizes or relies on a stored compressed gas. Upon actuation, such devices release the stored gas into an associated airbag cushion to effect the inflation thereof. While such inflator devices may reduce or avoid problems relating to particulate and hot gas discharges, such inflators generally require the potentially long-term storage of a material under pressure. As will be appreciated, such long-term pressure storage can raise concerns  regarding undesirable leakage over the course of the relatively long design lifetimes of such systems once installed in vehicles.
Yet another common form or type of inflator device utilizes or relies on a combination of stored compressed gas and combustion of a gas generating material, e.g., a pyrotechnic, to produce or form an inflation gas for an associated airbag cushion. Such an inflator device is commonly referred to as an augmented gas or hybrid inflator. As with the above-identified pyrotechnic inflators, such inflator devices may result in a gas having an undesirably large or high particulate content. Also, while the discharge from such a hybrid inflator device is generally at a reduced temperature as compared to a corresponding pyrotechnic inflator, the temperature of such discharge may still be undesirably high for certain applications. Further, such inflator devices may suffer from at least some of the possible complications and related concerns regarding the potentially long term storage of a material under pressure.
In view of the extensive familiarity and experience with hot gas-producing inflator devices such as pyrotechnic-based inflators, there has been a desire to apply or utilize pyrotechnic-based inflator devices in association with side impact inflatable restraints. Unfortunately, is not always easy or practical to compensate for the elevated temperature discharges typically associated with pyrotechnic-based inflator devices via the inclusion of a heat resistant coating or one or more patches of heat resistant material within an associated side impact inflatable  cushion element. For example, such inclusion almost invariably results in the side impact cushion, when folded such as in a stored condition, being more bulky than is generally desired. Moreover, inflatable restraints such as inflatable curtains which are commonly designed to provide protection over an extended area typically need to be rapidly inflated over relatively extended lengths, as compared to common front impact inflatable restraint devices. The provision of inflation gas produced by the reaction of pyrotechnic gas generant materials along extended lengths in a desirably uniform and rapid manner can be particularly challenging to achieve.
Thus, there is a need and a demand for inflator devices and associated assemblies and methods of use such as may more readily permit or facilitate the use of hot gas-producing inflator devices, such as pyrotechnic-based inflators, in association with inflatable devices designed to provide protection over an extended area, such as inflatable curtain inflatable devices.